1. Field of Invention
This invention relates to medical devices and instruments. More particularly, this invention relates to hemostasis valves and hemostasis cannula units containing a hemostasis valve, wherein the hemostasis valve is comprised of two separate valve members, a valve gasket and a complementarily shaped valve membrane, each of which has a different thickness.
2. Prior Art
The introduction of catheters into blood vessels for a variety of purposes such as coronary angiography has been known for many years. Several techniques for introducing these catheters into the vasculature of the human body are available. One such technique is the cut-down method, while another is the Seldinger technique. The Seldinger technique includes surgically opening a vein or artery with a needle, inserting a guidewire into the vessel through the lumen of the needle, withdrawing the needle, inserting over the guidewire a dilator which has passed through an associated sheath containing a hemostasis valve, removing the dilator and inserting a catheter through the hemostasis valve and sheath into the blood vessel.
A wide variety of hemostasis valves are known in the prior art. However, when a guidewire is inserted through most hemostasis valves, because the guidewire is so small relative to the catheters which may also be employed, it is difficult for the valve to seal adequately against the backward pressure of blood, while at the same time permitting easy insertion of much larger diameter catheters into the vasculature. This problem is particularly acute with catheterization procedures involving arterial invasion where there is a high reverse pressure of blood. In these arterial procedures, blood can squirt out when the guidewire is introduced through the hemostasis valve. Excessive blood leakage may be extremely dangerous to patients and a contaminant to physicians. Accordingly, most prior art hemostasis valves are designed for use with only one particular size of catheter. It has often been difficult to employ a single hemostasis valve with catheters of widely varying diameters because adequate sealing around the catheter walls cannot be achieved.
Cardiac catheter introducers used during coronary procedures often contain a hemostasis valve that is mounted in the valve housing or hub secured on the proximal end of the introducer. Such an introducer is conventionally used to facilitate the insertion of the catheters and guidewires into the vascular system of a patient, while minimizing injury to the patient at the access site and improving the patient's comfort during the cardiac catheterization procedure. An introducer is particularly necessary where one or more treating catheters of varying diameters are inserted into and removed from the patient's vessel repeatedly as occurs in angiographic procedures and angioplasty. The presence of the catheter introducer and the insertion of different size catheters often causes bleeding during cardiac catheterization procedures. A high performance hemostasis valve is therefore needed to seal against the leakage of blood out of or around catheters and guidewires having varying diameters as they enter an artery or other blood vessel. The hemostasis valve must also prevent the reverse seepage of air into the artery or blood vessel of the patient when one or more than one of the elongated catheters or guidewires are withdrawn from the introducer. In addition, the valve must remain sealed when there is no medical device passing through the valve. Accordingly, the requirements for a useful hemostasis valve include at least the following: (a) the valve is always sealed when no elongated cylindrical member is introduced into it; (b) the insertion and retraction forces must be minimal when larger diameter catheters (such as those larger than about 9 F (3 mm)) are introduced into the valve; (3) in contrast, the valve must maintain good sealability when small diameter guidewires (such as those down to 0.014 in. (0.35 mm)) pass through its passageway; and (4) to the greatest extent possible, the deformation of the valve must be in a radial direction instead of an axial direction to prevent the transmission of air into the blood stream.
Numerous hemostasis valves are known which can be classified in three major groups. Type I, as disclosed, for example, in U.S. Pat. Nos. 5,041,095 and 5,176,652, contain a pair of gaskets of approximately equal thickness. Each gasket has a Y-shaped opening cut into the gasket radially extending from its center forming three (3) slits, each located at an angle of about 120 degrees from the other slits. Each slit penetrates the gasket from one end face to the other end face. To form a self-sealing hemostasis valve, the two Y-shaped slits of the respective gaskets are mounted in a position opposite to one another in the valve housing.
Other types of hemostasis valves containing multiple disks which are approximately the same size and thickness are disclosed, for example, in U.S. Pat. Nos. 2,023,267; 4,000,739; 4,430,081; 4,655,752; 4,673,393; 4,895,346; 5,000,745; and 5,643,227. Each of these patents discloses a different combination of valve disks that are used to form the hemostasis valve. In some embodiments, one of the disks contains Y-shaped slits and the other disk contains a circular opening in the center of that disk.
Type II hemostasis valves as disclosed in U.S. Pat. Nos. 4,626,245; 4,629,450; 5,114,408; 5,149,327 and 5,167,637 and utilize a single sealing disk. The disk generally has a first slit that opens at only one end face and a second slit that opens at only the other end face. The two slits, which form a crisscross, intersect each other inside the disk. Other types of single sealing disk hemostasis valves with different shapes for the opening through that disk are disclosed, for example, in U.S. Pat. Nos. 4,705,511 (see FIG. 4); U.S. Pat. No. 4,798,594 and 4,895,565.
Type III hemostasis valves, as disclosed, for example, in U.S. Pat. Nos. 5,149,327; 5,207,656 and 5,520,655, are similar to Type II hemostasis valves, but differ in that only one slit (Y-shaped or +-shaped) penetrates from one end face to the other end face of the gasket.
Other types of hemostasis valves can be found in various patents such as in U.S. Pat. Nos. 4,610,655; 4,909,798 and 5,125,903. However, these hemostasis valves are generally designed for use with a particular size of medical device. Because adequate sealing around the elongated cylindrical medical devices using conventional hemostasis valves cannot be assured for a wide variety of devices, each having a different diameter, it has not been possible to utilize a single hemostasis valve with devices of widely varying diameters. Also, many of the prior art hemostasis valves exhibit various performance defects due to various structural features. For example, it may be difficult to manipulate an elongated cylindrical medical device through the passageway formed by automatically closed slits because no pre-guiding centering channel is provided. In addition, for Type I hemostasis valves, the deformation arising from the insertion of the elongated cylindrical medical device into the valve is generally in an axial direction rather than radially away from the opening. The introduction of the medical device creates an axial gap between the gaskets that may result in leakage of blood under blood pressure. For Type II hemostasis valves, such axial gaps are sometimes reduced by integrating the sealing function of two gaskets into a single gasket. With this integration the sealability seems to improve in comparison to Type I hemostasis valves. However, the insertion force necessary for insertion of medical catheters through the passageway of the valves dramatically increases because the deformation force for the two slits of the hemostasis valve is in opposition to one another and the friction at the intersecting location of the two slits inside the valves increases.
For Type III hemostasis valves, the insertion force may also be a problem. In addition, these valves often do not seal against the leakage of blood when a small-diameter guidewire passes through its slit passageway.
Further, the restitutive force created by the retraction of larger-diameter catheters may cause the seepage of air into the blood stream.
It has been recognized that axial deformation of the hemostasis valve should be limited to improve sealability. For example, U.S. Pat. No. 5,520,655 discloses a medical device wherein the valve is pre-deformed in an axial direction opposite to that of the insertion force. The axial deformation induced by the insertion of an elongated medical device is compensated for by this pre-deformation. As a result, the actual deformation during insertion seems to be radial to the valve, thus improving the sealability of the valve. However, the insertion force may increase due to this pre-deformation, and the restitutive force due to the retraction of the elongated cylindrical member may still allow the seepage of air into the blood stream.
U.S. Pat. No. 4,917,668 suggests the use of spring-loaded resilient gasket valve members with one or more spring elements augmenting the natural resilience of the sealing gasket material to improve sealability. However, the insertion force increases with incorporation of metal springs.
In yet another approach to providing a suitable seal under varying conditions encountered in practice, U.S. Pat. No. 5,125,903 discloses the use of concave and convex cusp-shaped surfaces to form the thinned central region of the valve, through which the short intersecting slits extend at a 45 degree angle to the 90 degree line of intersection.
The hemostasis valves described above represent departures from, and attempts to overcome deficiencies in, the flat-sided disk-shaped gaskets involving reduced diameter holes, slits and crossed slits therethrough to accommodate elongated cylindrical medical devices passing through the valve.
Accordingly, it is an object of the present invention to prepare a universal hemostasis valve which exhibits high performance in sealing against the leakage of blood, limiting the backflow of air into the vessels and easing insertion and retraction of elongated cylindrical medical devices of varying diameters. This hemostasis valve may be reliably used with a wide variety of both large catheters, up to about 9 F (3 mm), and small guidewires, down to 0.014 in. (0.35 mm).
It is a further object of the invention to disclose a hemostasis valve composed of a valve gasket and a separate valve membrane, wherein the valve gasket is thicker than the valve membrane.
It is a further object of the invention to disclose a hemostasis valve comprising a valve gasket and a valve membrane, wherein the valve membrane contains a positioning protrusion element which fits within a positioning slot of the valve gasket.
It is a still further object of the invention to disclose a hemostasis valve comprised of a valve gasket and a valve membrane, wherein the valve gasket contains a conical receiving area and a guiding hole to guide medical devices through the hemostasis valve.
It is a still further object of the invention to disclose a hemostasis valve, composed of a valve gasket and a valve membrane, wherein the valve membrane contains a beveled edge which interacts with a beveled edge of the valve gasket when blood pressure is placed on the hemostasis valve to convert the axial force of the blood to a radial force.
It is a still further object of the invention to disclose a hemostasis valve composed of a valve gasket and a valve membrane, wherein the valve gasket and the valve membrane maintain substantial contact against each other throughout the medical procedure.
It is a still further object of the invention to disclose a hemostasis cannula unit including a valve housing, a cap and a hemostasis valve, wherein the hemostasis valve is composed of a valve gasket and a valve membrane, wherein the valve gasket is thicker than the valve membrane.
These and other objects can be obtained by the disclosed hemostasis valve and hemostasis cannula unit which are disclosed by the present disclosure.